This application claims the priority of German Patent Application No. 198 33 366.8, filed Jul. 24, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a heat exchanger made of plastic having flow channels for guiding two fluids using the countercurrent principle, as well as a method for its manufacture and an air conditioning unit.
A heat exchanger made of a thin-walled plastic material is known from DE 39 12 628 A1, in which the heat exchanger consists of three elements separable from one another and using the countercurrent principle.
It is known from a brochure, xe2x80x9cPro Condensxe2x80x9d from Gxc3x6tz Heizsysteme GmbH, to provide a plastic heat exchanger associated with a steel heating boiler. The plastic heat exchanger operates using the countercurrent principle, with fresh air drawn in by the heating burner flowing in one direction and the hot exhaust gas flowing in the other direction. The fresh air supplied to the heating burner is thus already preheated. At the same time, the exhaust gas is cooled and partially condensed. The structure of the plastic heat exchanger is not described in this brochure.
The object of the present invention is to provide a heat exchanger that ensures a simple and functionally reliable transfer of heat.
This object is achieved by virtue of the fact that the exchanger is made in three parts, namely a cover part, an intermediate layer that at least partially forms the flow channels, and a trough part, with the intermediate layer being made in one piece and provided with flow sections, spaced apart from one another and open at a front, of the flow channel for the first fluid in such fashion that the opposite sections remaining between the channel sections automatically form the flow channel of the second fluid guided in the opposite direction, with the wall areas separating the channel sections and opposite sections being designed as heat transfer membranes, and that the cover part and the trough part are connected with the intermediate layer tightly in such fashion that the flow channels and opposite sections are combined to form the flow channels for the two fluids. The term xe2x80x9cfluidxe2x80x9d according to the present invention refers to both gases and liquids.
As a result, in simple fashion, by means of only a single intermediate layer, the arrangement of one flow channel and an appropriately opposed flow channel is created. The channel sections are designed as heat transfer membranes such that the wall areas between the channel sections and the opposite sections permit sufficient heat transfer between the fluids flowing in opposite directions. This heat transfer function can be produced by appropriate thinness of the walls, by the use of additional membranes, and/or by suitable flow guides such as turbulence elements or the like. The heat transfer membranes can also be formed by appropriate profiles so that the adjacent fluids have sufficient time for the respective heat transfer through the wall areas. Preferably, the flow channels are guided meanderwise or in zigzag fashion so that the flow sections or channel sections are each located between the other channel sections or opposite sections. The closed flow channels on both sides are produced by the respective tight connection of the cover part and the trough part.
In an embodiment of the present invention, the intermediate layer is designed as a deep-drawn part and the wall areas are deep-drawn thin walls such that there is a sufficient heat transfer between the fluids as they flow countercurrently. This is an especially simple design of a heat transfer membrane.
In another embodiment of the present invention, the cover part and the intermediate layer are manufactured jointly in a twinsheet method. This is an especially simple and sturdy type of manufacturing that ensures a high rigidity of the heat exchanger and a tight connection between the cover part and the intermediate layer. In the twinsheet method, two plastic plates, in this case the plates for the cover part and intermediate layer, are thermally shaped jointly by deep drawing and then thermoset in the desired shape.
In another embodiment of the present invention, the wall areas are provided with turbulence profiles. Heat transfer is further improved as a result.
For good heat insulation and transfer, the cover part, the intermediate layer, and the trough part are dark in color, preferably black.
In another embodiment of the present invention, the channel sections and the correspondingly designed opposite sections are each guided zigzag-wise, thereby producing U-shaped reversing areas as a result. This is an especially advantageous design of the channel sections and the opposite sections, since a considerable length of the flow channels and therefore a large heat transfer area is produced on a comparatively small surface. Good heat transfer also permits a compact design.
In another embodiment of the present invention, the flow channels in the vicinity of the reversing areas have at least the same flow cross sections as in the vicinity of the associated channel or opposite sections. As a result, at least largely constant flow pressure conditions are achieved for both flow channels, thus guaranteeing reliable and functionally safe operation of the heat exchanger.
In another embodiment of the present invention, the cover part and/or the trough part are releasably connected with the intermediate layer. This makes it possible to remove impurities from inside the heat exchanger. Especially advantageously, the intermediate layer can be separated from the trough part, since condensate and impurities in the condensate collect in the trough part and can be removed in simple fashion from time to time.
In another embodiment of the present invention, the cover part and trough part are shaped relative to one another in such fashion that two or more three-part heat exchanger units can be stacked on top of one another. This is especially advantageous if the heat exchanger is subjected to high flow volumes or greater temperature differences between the fluids which could not be sufficiently modified by a single unit. Stacking several heat exchanger units makes it possible to produce a compact design of the resultant total heat exchanger with improved heat transfer.
In another embodiment of the present invention, the connecting openings in the cover part and in the trough part are shaped to correspond to one another in such fashion that with at least two heat exchanger units stacked on top of one another, the corresponding connecting openings of the cover part and adjacent trough part can be inserted into one another. Additional connections between the heat exchanger units on top of one another are thus avoided.
Air conditioning units formed by decentralized ventilation systems including heat recovery for residences and businesses are generally known. However, in addition to a large amount of space, these also require a high installation cost.
Another object of the present invention is thus to create an air conditioning unit for enclosed spaces, especially residences and businesses, which can function with the lowest possible installation cost.
This object is achieved according to the present invention by an air conditioning unit for enclosed spaces that has (1) an air intake associated with a first connection of the room interior with an outside environment; (2) an air outlet spaced apart from the air intake which is associated with a second connection of the room interior to an outside environment; and (3) a fan arrangement associated with the air intake and/or the air outlet. Both the air intake and the air outlet are connected to a heat exchanger according to the present invention.
As a result, using the heat exchanger according to the present invention, it is possible to provide, in a simple manner, room ventilation with heat recovery and air conditioning as a function of the outside and inside climatic conditions. By using the countercurrent heat exchanger, an extremely low installation cost is required since the corresponding heat exchanger can be positioned directly in the vicinity of a wall of the respective room and requires only a matching number of passages through the wall to the outside. In addition to heat recovery in cold seasons, use of the heat exchangers in air cooling systems is especially advantageous. In this case, the room air expelled to the outside, with corresponding ventilation and already cooled by the air conditioning system, can serve to precool the warm outside air from the environment as it flows in on the intake side. As a result, considerable energy savings are realized since the incoming outside air has already undergone a certain amount of pre-cooling in the heat exchanger by transferring heat to the outgoing room air.
In designing this invention, the fan arrangement can be operated by a control or regulating unit. The control or regulating unit may contain open loop control units, closed loop control units, and feed-back control units. As a result, the air intake and air exhaust for the respective room can be controlled. Preferably, the regulating unit has at least one actual-value sensor located in the air intake and/or exhaust whose signals can be compared with at least one set-point adjuster, and the fan arrangement can be controlled as a function of the result of this comparison. The at least one actual-value sensor is designed especially for temperature, humidity, and carbon dioxide content determination in the incoming and/or outgoing air. Preferably the set-point adjuster is part of a microprocessor unit to which a plurality of actual-value sensors for different types of data acquisition can be connected. By using a basically known volume flow measurement, depending on the corresponding parameters, the air volume can be regulated and extremely uniform energy-saving room air conditioning can be performed.
In another embodiment of the present invention, a filter arrangement is associated with the air intake. This can consist of a simple protective grid for keeping out coarse dirt and insects; a nonwoven grating with electrostatic properties for binding dust and pollen; an activated charcoal filter for trapping harmful gases and aerosols; or even a high-voltage filter composed of capacitor plates charged to approximately 10 kV for trapping very fine dust and bacteria. Preferably, the filter arrangement is located replaceably in a housing of the heat exchanger. As a result, the filter inserts can preferably be removed by appropriate plug connections and cleaned or replaced.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.